Purchase now: Allen-Bradley 1756-ENBT EtherNet/IP Module
Purchase now: Atlantechdrives provides you the 1756-ENBT, a highly dependable, legacy-generation EtherNet/IP communication bridge module engineered by Rockwell Automation for the widely installed ControlLogix 1756 programmable automation platform. While newer manufacturing facilities lean towards the high-capacity EN2T or EN3TR models, the 1756-ENBT remains an incredibly sought-after component for maintaining and repairing existing, validated industrial systems. In strictly regulated industries—such as pharmaceutical manufacturing (FDA 21 CFR Part 11) or continuous nuclear power generation—engineers cannot simply upgrade to a newer module model without triggering massive, incredibly expensive software re-validation protocols. The 1756-ENBT serves as the exact, «like-for-like» hardware replacement, allowing maintenance technicians to rapidly swap a failed module and restore factory production without altering a single line of PLC code or updating network hardware configurations. Featuring a single 10/100 Mbps RJ45 copper port, it routes critical I/O data, HMI screen updates, and peer-to-peer processor interlocking messages safely across the factory floor network.
Technical Specifications of the 1756-ENBT
As a first-generation EtherNet/IP bridge, the 1756-ENBT possesses specific processing limitations compared to its modern successors, making it ideal for standard I/O routing and HMI communication rather than massive multi-axis CIP motion networks.
- Part Number: 1756-ENBT
- Platform: ControlLogix 1756 System
- Network Protocol: EtherNet/IP
- Embedded Ports: 1 x RJ45 (10/100 Mbps, Half/Full Duplex)
- Connection Capacity: 64 TCP/IP connections, 128 CIP connections
- Packet Rate: Up to 5,000 I/O packets per second
- Backplane Current Draw: 700 mA at 5.1V DC; 3.0 mA at 24V DC
Expert Tips: TCP/IP Connection Limits and Network Overloading
When working with legacy hardware, understanding connection constraints is vital to prevent mysterious network crashes. Expert Tip: The 1756-ENBT is strictly limited to 64 TCP/IP connections. Every time a PanelView HMI, a SCADA server, an engineering laptop running Studio 5000, or a remote Variable Frequency Drive connects to this module, it consumes one of those connections. If your IT department attempts to aggressively poll the ControlLogix processor for manufacturing data using third-party OPC servers, you can easily max out this 64-connection limit. When the limit is reached, the 1756-ENBT will simply refuse new connections, causing HMIs to drop offline or «freeze.» Always monitor the diagnostic connection count on the module’s scrolling alphanumeric display to ensure you are not bottlenecking your automation network.
Installation Advice: IP Address Assignment via BOOTP/DHCP
Unlike modern Ethernet modules that feature a USB port for quick configuration, the 1756-ENBT requires a network-based initial setup. Out of the box, the module defaults to BOOTP/DHCP mode, meaning it actively broadcasts its MAC address on the network looking for an IP assignment. You must use the Rockwell BOOTP-DHCP Server utility software on a laptop connected to the same subnet. Once the software detects the module’s MAC address (which is physically printed on the side sticker of the module), you assign the static IP address and, most importantly, click «Disable BOOTP/DHCP.» If you forget to click disable, the module will lose its IP address the next time the factory loses power, completely crashing your network upon reboot.
Frequently Asked Questions (FAQs)
Q: What does the scrolling text on the front of the 1756-ENBT mean?
A: The alphanumeric display is a critical diagnostic tool. During normal operation, it scrolls «OK» followed by its assigned IP address. If it flashes «Link Lost,» the physical Ethernet cable is unplugged. If it flashes «Duplicate IP,» another device on your factory network is incorrectly using the same IP address.
Q: Can I use the 1756-ENBT to control Kinetix Servo Drives using CIP Motion?
A: No. The 1756-ENBT hardware does not support the precise time-synchronization (IEEE 1588 CIP Sync) required for integrated motion control. If you are doing CIP motion over Ethernet, you must upgrade to at least a 1756-EN2T or EN3TR.
Do you need more references from this brand? Explore our full catalog of Allen-Bradley here.
This standard EtherNet/IP bridge provides a reliable network link when housed in a medium-sized 1756-A7 7-slot chassis.
